TextInput expands parent container unexpectedly

### Current behaviour
TextInput inside a flex container without width constraints, the input expands to full width, causing the parent container to stretch. Expected behavior is that it should respect the parent’s intrinsic size unless explicitly styled.

### Expected behaviour
Expand the parent container

No source file or test is named. Start by reproducing TextInput inside an unconstrained flex container and compare the current and intended sizing; clarify the contradictory expected-behavior text before locating the component implementation and adding a regression test for the agreed intrinsic-size behavior.

Written by the indexing model from the issue text.